1. Field of the Invention
The present invention relates to a grinding method for grinding the back side of a wafer such as a semiconductor wafer to thin the wafer to a predetermined thickness, and particularly to an improving technology for minimizing the chipping of the outer peripheral edge of a wafer generated when the back side of the wafer is ground.
2. Description of the Related Art
In general, semiconductor chips of devices used for various electronic apparatus are each produced by a method in which rectangular regions are demarcated on the face side of a circular disk-like semiconductor wafer in a lattice pattern by planned splitting lines, electronic circuits such as ICs and LSIs are formed on the face side of these regions, then the back side of the wafer is ground to thin the wafer, and the wafer is cut and split (diced) along the planned splitting lines.
Meanwhile, since the wafer with its back side to be ground is preliminarily subjected to chamfering of the outer peripheral edge, the outer peripheral edge becomes knife edge-like in sectional shape after the wafer is thinned to or below one half of the original thickness, and, therefore, the outer peripheral edge is liable to be chipped during grinding. The chipping of the outer peripheral edge becomes a starting point of breakage, thereby serving as a major cause of lowering in the yield of the wafer; therefore, there is a need to restrain the chipping as securely as possible. In view of this, there is known a technology for restraining the generation of chipping by removing the knife edge-like outer peripheral edge at a stage before grinding (refer to Japanese Patent Laid-open No. 2003-273053 and Japanese Patent Laid-open No. 2006-108532).
According to the technology in the related art, the removal of the outer peripheral edge of a wafer before grinding is conducted by cutting in with a cutting edge of a dicing device or by irradiation with a laser beam using a laser beam machining device. Each of these devices is separate from the wafer grinding device, so that the wafer before being ground is set onto the device and its outer peripheral edge is removed, before the wafer is set onto the grinding device. More specifically, the step of removing the outer peripheral edge of the wafer at a stage before grinding of the back side of the wafer is added, and a device for this purpose is needed, which leads to a lowering in productivity and a rise in cost.